Millimeter-wave bands are of increasing interest for the satellite industry and potential 5G bands. Multi-element antennas for 5G applications make use of these high frequencies to incorporate a large count of radiating elements. These antenna arrays are essential for beamforming operations that play an important part in such next generation networks.
Presently one is unable to fully and directly measure and characterize a multi-element antenna, for example, one used in beamforming applications. Many parameters must be estimated or calculated from a basic measurement on one element. A theoretical calculation is not a measurement verification.
Characterization of a multi-element antenna generally requires at least two procedures: Measurements based on S-parameters (e.g., return loss, cross-coupling between elements, etc.), and Pattern Measurement, including Beam Steering and complex Beam Formation.
For pattern measurement, the prior art is to excite a single antenna element and measure the single-element beam pattern. Such an approach is described in the Rohde & Schwarz Application Note “Characterizing Active Phased Array Antennas,” August 2016, which can be obtained from the website https://www.rohde-schwarz.com/appnote/1MA248, and is incorporated by reference herein. The Beam Steering weightings and Complex Beam Formation are then calculated theoretically, but are not measured and therefore not verified.
Especially in multi-element arrays with few elements, the theoretical calculations can be heavily in error. Generally, this is because the extreme elements behave differently.